1. Field of the Invention
The present invention relates to the use of fluorochemical surfactants in coating compositions to reduce disuniformities in the coatings. The surfactants reduce such effects as mottling without causing such side effects as fisheye and foaming in the coated materials. These surfactants are particularly useful in graphics systems such as positive-acting or negative-acting resist systems including printing plates and non-resist imageable polymerizable systems.
2. Background of the Art
There are many different types of coating operations that use organic polymeric resins in the coating solutions. The polymers are normally coated out of a solid solution and dried by the removal of most of the solvent. Many of the defects and problems that occur in the final product can be attributable to phenomena that occur in the coating and drying procedures. Amongst the problems that are known to occur during drying of polymeric film layers after coating are unevenness in the distribution of solid materials within the layer. Examples of specific types of problems encountered in coatings are "orange peel" and "mottling." The former is a fairly regular grainy surface that occurs on a dried coated film, usually because of the action of the solvent on the materials in the coating composition. Mottling often occurs because of an unevenness in the removal of the solvent from the coating composition. "Fisheyes" are another type of coating problem, usually resulting from a separation of components during drying. There are pockets of different ingredients within the drying solution, and these pockets dry out into uneven coating anomalies.
Surfactants have often been used to correct these types of problems, along with changes in the solvents of the coating compositions. Sometimes surfactants do not correct the salient problem, and in other cases, the surfactants create other problems even when they cure the first. It is sometimes necessary to investigate a large number of commercially available surfactants before finding one that is appropriate for a particular type of system, even if that commercial product is touted for use in correcting a particular type of defect.
U.S. Pat. Nos. 4,764,450 and 4,853,314 describe the use of particular changes in solvent systems to improve surface defects in positive-acting photoresist imaging systems.
U.S. Pat. No. 4,557,837 describes fluorochemicals useful in the preparation of foamable compositions such as those used in the cleanup of gas wells. The polymers described within that patent include some compounds useful in the practice of the present invention.
U.S. Pat. No. 3,950,298 describes thermoplastic fluorinated terpolymers that are useful, non-foaming additives to coating solutions for polymeric materials such as carpets and fibers. The coating compositions provide oleophobicity to the surfaces that are coated.